<body>
  <div id="el" style="width:100px; height:100px; background-color:red;display:inline-block"></div>
  <div id="el2" style="width:100px; height:100px; background-color:green;display:inline-block"></div>
  <div id="el3" style="width:100px; height:100px; background-color:blue"></div>
  <button id="pause-btn">pause</button><button id="resume-btn">resume</button><button id="reset-btn">reset</button>
  <script type="module" src="./animation-demo.js"></script>
</body>